Department of Homeland Security Secretary John Kelly did such an efficient job implementing Donald Trump’s anti-immigration agenda that he’s getting promoted. Trump announced in a surprise tweet Friday afternoon that Kelly will replace Reince Priebus as White House chief of staff.

“John has done a spectacular job at Homeland Security,” Trump tweeted. “He has been a true star of my Administration.”

Indeed, in the last six months, Kelly has turned the DHS into one of the most productive arms of the Trump administration. Kelly managed to translate much of Trump’s brazen anti-immigrant campaign rhetoric into actual policy. And if the numbers are any indication, Kelly has certainly flourished. Arrests since Trump took office in February increased by 40 percent over the prior year. But perhaps more important than the numbers is Kelly’s impact on immigrant communities, where apprehension and fear now reign.

Here’s a roundup of the key policy changes that Kelly has ushered in, in just six months on the job:

1) Ending prosecutorial discretion for undocumented immigrants.

In a sweeping February memo, Kelly did away with the Obama-era policy of prioritizing the deportation of those who’d been convicted of serious crimes. On paper (if not always in practice), the Obama administration directed immigration agents to focus their energy on those who’d been convicted of serious crimes and to largely leave alone those who’d been convicted of no crimes. In February, Kelly wrote: “Unless otherwise directed, Department personnel may initiate enforcement actions against removable aliens encountered during the performance of their official duties.” Translation: Every undocumented and deportable immigrant would now be fair game.

Gone are the tiers of enforcement that the Obama administration put forth. Even as Trump himself says that he wants to rid the country of the “rapists” and “murderers” among the immigrant population, Kelly has pursued a policy that targets all undocumented immigrants. Kelly’s policy effectively blurs the line between who is an “immigrant” and who is a “criminal”—despite what Trump says. On a practical level, immigration agents no longer have to think carefully about whether an undocumented immigrant they come across is a priority, because anyone who’s undocumented can go. As a result, those with no criminal records or those with the most minor of infractions are as much at risk as those with serious convictions.

Trump’s supporters have taken him at his word. “I think our president is going to keep all the good people here,” Helen Beristain, a Trump voter, told CNN this spring, as her husband, Roberto Beristain, faced deportation. He had not been convicted of a crime. “He’s not going to tear up families. I don’t think he wants to do that. He just wants to keep us safe,” Beristain said of Trump. Roberto was later deported.

2) Redefining who a “criminal alien” is.

In those same February memos, Kelly also expanded the notion of a “criminal alien.” Now a “removable alien” is anyone who has been convicted of a crime, been charged with a crime, or even committed anything that might be a “chargeable criminal offense” (jaywalking, anyone?). Immigrants who committed any kind of fraud (like using a fake Social Security number) or abused any public benefit would also be a priority for deportation, alongside anyone who had an order of removal that they’d ignored. But perhaps most stunning, Kelly directed the department to pursue anyone who, “in the judgment of an immigration officer,” posed a national-security risk to the country. In other words, any and every immigrant could be targeted by an immigration official.

This change blew the doors wide open and has resulted in high-profile incidents of longtime undocumented immigrants’ being detained during routine check-ins, such as Guadalupe Garcia de Rayos, a Phoenix mom who was deported in February after an immigration check-in. In 2008, Garcia de Rayos was arrested during a raid at the water park where she worked. She was caught using a fake Social Security number, and far from hiding afterwards, the longtime Arizona resident faithfully went to every check-in at a local ICE office since then.

The effect of Kelly’s memos has been to offer immigration agents new freedom to go further into communities to detain and arrest immigrants. Far from nabbing criminal masterminds, ICE agents have instead been reaching for the most vulnerable undocumented immigrants. In February, ICE agents turned up at a Texas courthouse and detained a woman fleeing domestic abuse. She was there seeking a protective order against her boyfriend, but left under arrest by ICE. Also in February, ICE agents waited outside a Virginia church’s hypothermia shelter and arrested two men. In May, ICE agents crossed an unspoken line regarding immigration-law enforcement when they entered P.S. 58, a Queens, New York, elementary school, to inquire about a fourth grader.

3) Calling for the revival of 287(g).

Most interior immigration-law enforcement—that is, enforcement that happens away from the border—depends on the cooperation of local law-enforcement agencies. There simply are not enough federal resources to pursue every undocumented immigrant that the Trump administration would like to pursue. In order to accomplish Trump’s goals, Kelly called for a return to old programs, like 287(g), which deputizes local and state police officers to act as immigration agents.

Together with Jeff Sessions’s pressure on sanctuary cities, the two are bearing down on localities that want to keep the work of public safety and immigration-law enforcement separate. Already, police arrests funnel undocumented immigrants into the deportation system. But under Kelly and Sessions, increasingly, police have become immigration agents.

4) Ending DAPA.

DAPA (Deferred Action for Parents of Americans and Lawful Permanent Residents) refers to a never-implemented program from the Obama years which would have offered the parents of undocumented DREAMer youth and green-card holders short-term protection from deportation. Last month, Kelly formally dismantled the program.

DAPA was an expansion of the successful initiative DACA, or Deferred Action for Childhood Arrivals, which gave select undocumented young people work permits and protection from deportation for two years. Nearly 800,000 young people have taken advantage of the program, which allowed them to get jobs, pursue education, and build their careers. It’s also been good for the economy. A Center for American Progress survey found that 20 percent of surveyed DACA recipients bought a car after obtaining DACA, and that one in 12 even bought a home. DAPA, however, got stalled in the courts after dozens of states led by Texas sued the Obama administration. The program would have benefitted an estimated 4 million undocumented immigrants, but the Trump administration decided not to defend the program in court.

5) Weighing the expanded use of expedited removal.

This month, a leaked DHS memo revived an idea which was originally tucked into Kelly’s original February memos. The memo called for expanding the use of expedited removal, which is the practice of bypassing immigration courts and summarily shoving people out of the country. As of 2004, its use was limited to those who were apprehended within 100 miles of the US-Mexico border and who couldn’t prove that they’d been in the country for more than two weeks.

The new proposal would greatly expand the policy to include anyone apprehended anywhere in the country who hadn’t been in the United States for more than 90 days. This policy change would hand immigration officers even more power over the fates of the people they detain. This, to be clear, is just a proposal. But even in 2013, 44 percent of removals happened via expedited removal.

If Kelly’s short tenure is any indication, his elevated role as White House chief of staff will be a disaster for immigrants, never mind who replaces him at Homeland Security, a process in which he will undoubtedly play a large part.